*3.2.1. Stress-free birds*

All types of stresses mentioned earlier should be avoided before administration of vaccines to poultry birds. The temperature of the environment and sheds should be normal before vaccination. Moreover, the birds should be in a good physical condition before administration of vaccines. Stress suppresses the chicken's immune response, and during these conditions of stress, birds should not be vaccinated [41]. The stress on birds can be minimized by the use of vitamins and minerals in drinking water before, during and after vaccination [13].

#### *3.2.2. Deworming before vaccination*

The adult birds may be dewormed before vaccination at least 15 days before injection of vaccine; moreover, diseased birds should be treated properly and be given vaccines after recovery. Only healthy flocks should be vaccinated.
